Electronic equipments are the heart of many modern systems and especially of today's communications systems. Traditionally such equipments were large and bulky, including using mechanical elements such as relays. Today the equipments tend to be smaller and compact, using semiconductors and optical elements. This has meant that central offices for telephone systems no longer use large and high equipment frames with spacing between equipments but now are being designed with smaller equipment frames or cabinets with the components more compactly mounted and with heat dissipation of more concern than in the past.
Further the concentration of electronic components has increased concerns over the reliability and survivability of the equipment when catastrophic conditions occur, such as earthquakes. It is axiomatic that if an earthquake occurs the need for effective and operational communications systems is the greatest.
Two basic structures are generally used to support electronics equipment in central offices; these are the frame and the cabinet, both of which may be generically referred to as equipment enclosures.
Equipment frames used to support electronics equipment typically utilize two uprights welded to a base having facilities for fastening to a concrete floor. A horizontal crossmember welded to the two uprights provides additional frame stiffness and a support for cable. The uprights are typically open-channel construction that may be used for routing signal cable. The base of the frame is enclosed for routing power cable.
Frame bases generally have narrow depths causing them to be unstable, especially when heavily loaded and/or subject to earthquake shocks. The overall strength of the frame is generally limited by the cross-section and dimensions of the uprights and the strength and positions of the concrete anchors. Their tall, open construction shape causes most frames to be flexible in the side-to-side direction. They therefore depend upon the stiffness and placement of the installed electronics or upon specially located stiffeners and bracing members for additional overall strength.
Typical equipment cabinets consist of four uprights that form a rectangular box-like frame for supporting the equipment. The uprights are connected to an outer sheet-metal face on each side. Provisions for the attachment of both front and rear doors are generally made. As with the frames, the strength of the typical cabinet is limited by the uprights. These uprights are often not directly connected at the top or the base, and in such instances the load of the equipment within the cabinet is not transferred to the structure of the cabinet. Additional loss of strength may be expected if the top or base is cut away to provide cable access.
Typical of the prior art approach to increasing the strength of the equipment cabinet or frame against major stresses, such as earthquake shocks, is the complicated use of special support members, as in Sevier et al patent 5,004,107, issued Apr. 2, 1991. Such apparatus involves complicated manufacturing steps and additional bracing elements. The manufacturing of such enclosures thus involves a large number of process steps in order to provide the required features, including cable routing, fastening equipment shelves, and the desired strength and earthquake resistance reliability. Further, these prior enclosures are generally designed for installation on either concrete floors or raised floors, but not both. Installations on raised floors require deep bases for stability and may require cables to enter the frame or cabinet from overhead. Prior enclosures do not generally provide for either overhead or underfloor cable routing in a single design.